It is known that operation of PEM (polymer electrolyte membrane) fuel cells for extended periods (several hundred or more hours) results in performance decay; that is, a reduction in output voltage at any given current density. It is also known that operating the fuel cell without oxidant tends to rejuvenate the fuel cell so that its performance is at least substantially recovered as is described, for instance, in U.S. Pat. No. 4,294,892. In PCT International Publication No. WO 01/01508, rejuvenation is carried out while the fuel cell continues to generate power by causing oxidant starvation of only a portion of each cell at any moment, or by periodic momentary oxidant starvation of all cells such that the interruption of power to the load is deemed to be inconsequential. However, evidence therein suggests that the rate of decay following such rejuvenation procedures is worse, further suggesting that this is not a long-term solution to the performance decay problem.